The Demand Charge Problem at Fleet Scale
A fleet operator converting 50 diesel delivery vehicles to EVs faces a charging infrastructure challenge that has no equivalent in the ICE world. If all 50 vehicles return to the depot at 7 pm and plug in simultaneously, the instantaneous load reaches 500 kW–1 MW depending on charger power levels. For a facility on a commercial HT supply with a sanctioned load of 300 kW, this means either a costly connection upgrade or vehicles that cannot charge.
More insidiously, even a single hour per month where depot load exceeds the sanctioned demand causes a demand charge penalty that can run ₹150–300/kVA — applied to the entire month's billing. A fleet operator who does not manage charging carefully can easily add ₹8–20 lakhs/year in demand charges on top of the base energy cost, erasing the fuel savings that motivated the electrification decision in the first place.
How Smart Scheduling Solves This
Managed EV charging at a depot works by treating the charging window — typically 7 pm to 6 am for overnight operations — as a resource allocation problem. The EMS receives three inputs for each vehicle: state of charge at plug-in, required departure SoC, and scheduled departure time. It then calculates the minimum power allocation needed for each vehicle to reach its target SoC before departure, staggering sessions to keep total depot load within the sanctioned maximum throughout the night.
- A vehicle returning with 30% SoC and departing at 7 am has 11 hours — it can charge at a relatively low rate and its session can be deferred to the cheapest off-peak window.
- A vehicle with 15% SoC and an urgent 5 am departure has less flexibility and gets priority access to available capacity.
- A BESS co-located at the depot can absorb cheap off-peak grid energy and dispatch it during periods when multiple vehicles need simultaneous charging, further smoothing the load profile.
Industry case studies from fleet depot charging deployments in India show that smart scheduling typically reduces the peak demand registered at the meter by 60–75% compared to unmanaged charging — often eliminating the need for a connection upgrade entirely and avoiding demand charge penalties worth ₹5–15 lakhs/year for a 50-vehicle depot.
EVBooth's Approach to Fleet Depot Charging
EVBooth's CSMS includes a depot scheduling module built on OCPP 2.0.1 Smart Charging, which handles exactly this multi-vehicle prioritisation logic. Our EMS layer adds BESS coordination and solar integration for depots with co-located generation. For fleet operators evaluating electrification, we offer a pre-deployment modelling service — if you share your fleet size, duty cycles, and existing electrical infrastructure, we can model the charging load profile, required connection capacity, and BESS sizing before you commit to any capital expenditure.